5_python_while_loops_answers.ipynb

{
 "cells": [
  {
   "cell_type": "markdown",
   "id": "19464cb9",
   "metadata": {},
   "source": [
    "# Python While Loops Answers\n",
    "\n",
    "Practice exercises for for using while loops with Python.\n",
    "\n",
    "## Prerequisites\n",
    "\n",
    "In order to complete these exercises, you should know how to:\n",
    "- Create variables\n",
    "- Use print statements (to print strings and variables)\n",
    "- Use basic mathematic operators (`+`, `-`, `*`, `/`, `%` etc.)\n",
    "- Use relational operators ( `>`, `<`, `==`, `>=`, `<=`, `!=`)\n",
    "- Use logical operators (`and`, `or`, `not`)\n",
    "- Use input() to collect user input\n",
    "- Create functions\n",
    "- Use if, else and elif statements\n",
    "- Use while loops"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "40521b97",
   "metadata": {},
   "source": [
    "### Exercise 0\n",
    "\n",
    "Create a variable `num` that has a value of 12. Then write a while loop that prints every number from 1 up to that number.\n",
    "\n",
    "Hint: you need to create another variable as well as `num`."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "id": "e2f9536b",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "1\n",
      "2\n",
      "3\n",
      "4\n",
      "5\n",
      "6\n",
      "7\n",
      "8\n",
      "9\n",
      "10\n"
     ]
    }
   ],
   "source": [
    "## ANSWER EXERCISE 0\n",
    "\n",
    "num = 12\n",
    "\n",
    "i = 1\n",
    "while i <= num:\n",
    "    print(i)\n",
    "    i+=1"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "5cc9cee9",
   "metadata": {},
   "source": [
    "### Exercise 1\n",
    "\n",
    "Create code that prompts a user to enter a whole number that higher than 10. Use a while loop to repeatedly prompt the user until a valid number is entered.\n",
    "\n",
    "Test the code thoroughly by entering valid and invalid whole numbers and checking that the loop operates correctly."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "53e28528",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Enter a number that is higher than 10: 5\n",
      "Enter a number that is higher than 10: 9\n",
      "Enter a number that is higher than 10: 10\n",
      "Enter a number that is higher than 10: 12\n"
     ]
    }
   ],
   "source": [
    "# ANSWER EXERCISE 1\n",
    "\n",
    "num = 0\n",
    "\n",
    "while num <= 10:\n",
    "    num = int(input(\"Enter a number that is higher than 10: \"))"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "a208db01",
   "metadata": {},
   "source": [
    "### Exercise 2\n",
    "\n",
    "The code below generates a random whole number between 0 and 10\n",
    "\n",
    "Create code with a while loop to prompt the user to guess the number until the correct number is guessed. Give clues each time like \"higher\" or \"lower\". Print an appropriate message when the number is guessed."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "id": "c50e9072",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Guess the number between 1 and 10: 2\n",
      "The number is lower than 2\n",
      "Guess the number between 1 and 10: 1\n",
      "You got it!\n"
     ]
    }
   ],
   "source": [
    "import random\n",
    "num = (random.randint(1,10))\n",
    "\n",
    "# ANSWER EXERCISE 2\n",
    "\n",
    "guess = 0\n",
    "\n",
    "while guess != num:\n",
    "    guess = int(input(\"Guess the number between 1 and 10: \"))\n",
    "    if guess == num:\n",
    "        print(\"You got it!\")\n",
    "    elif guess < num:\n",
    "        print(\"The number is higher than\", guess)\n",
    "    else:\n",
    "        print(\"The number is lower than\", guess)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "13ba7556",
   "metadata": {},
   "source": [
    "### Exercise 3\n",
    "\n",
    "Create Python code that receives a number as an argument, and then prints a countdown based on that number. For an argument of 5 it should print:\n",
    "\n",
    "```\n",
    "Counting down...  \n",
    "5  \n",
    "4  \n",
    "3  \n",
    "2  \n",
    "1  \n",
    "Go!   \n",
    "```\n",
    "\n",
    "Use a while loop in your function. You do not need to validate user input: just assume they enter a valid number.\n",
    "\n",
    "\n",
    "### Going further \n",
    "\n",
    "Rewrite your code as a function called `countdown()` that receives the number as an argument and prints the countdown, with no user input or error checking."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "5393aa66",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Enter a whole number: 5\n",
      "Counting down...\n",
      "5\n",
      "4\n",
      "3\n",
      "2\n",
      "1\n",
      "Go!\n"
     ]
    }
   ],
   "source": [
    "# ANSWER EXERCISE 3\n",
    "\n",
    "num = int(input(\"Enter a whole number: \"))\n",
    "\n",
    "print(\"Counting down...\")\n",
    "while num >= 1:\n",
    "    print(num)\n",
    "    num-=1\n",
    "print(\"Go!\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "id": "dd73430e",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Counting down...\n",
      "5\n",
      "4\n",
      "3\n",
      "2\n",
      "1\n",
      "Go!\n"
     ]
    }
   ],
   "source": [
    "# ANSWER EXERCISE 3 GOING FURTHER\n",
    "\n",
    "def countdown(num):\n",
    "    print(\"Counting down...\")\n",
    "    while num >= 1:\n",
    "        print(num)\n",
    "        num-=1\n",
    "    print(\"Go!\")\n",
    "\n",
    "countdown(5)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "d581b44f",
   "metadata": {},
   "source": [
    "### Exercise 4\n",
    "\n",
    "Write Python code that receives a whole number from user input. The number must between 1 and 50 (print an error if the number is higher or lower). Then, based on that number, print the square of numbers from 1 to the input number.\n",
    "\n",
    "For an input of 5, the function should print:\n",
    "\n",
    "```\n",
    "The square of 1 is 1\n",
    "The square of 2 is 4\n",
    "The square of 3 is 9\n",
    "The square of 4 is 16\n",
    "The square of 5 is 25\n",
    "\n",
    "```\n",
    "\n",
    "For an argument of 52, it should print:\n",
    "\n",
    "```\n",
    "Error: The number must be 50 or less\n",
    "```\n",
    "\n",
    "Going further: Rewrite the code so that if the user enters a number that is higher or lower than 50, they are prompted to keep entering until a correct number is entered and its squares are printed."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "id": "aaef32c4",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Enter a whole number between 1 and 50: 5\n",
      "The square of 1 is 1\n",
      "The square of 2 is 4\n",
      "The square of 3 is 9\n",
      "The square of 4 is 16\n",
      "The square of 5 is 25\n"
     ]
    }
   ],
   "source": [
    "# ANSWER EXERCISE 4\n",
    "\n",
    "num = int(input(\"Enter a whole number between 1 and 50: \"))\n",
    "\n",
    "if num>50 or num<1:\n",
    "    print(\"Error: The number must be between 1 and 50.\")\n",
    "else:\n",
    "    i=1\n",
    "    while i<=num:\n",
    "        print(\"The square of\", i, \"is\", i*i)\n",
    "        i+=1"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "id": "d749006b",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Enter a number between 1 and 50: 51\n",
      "Enter a number between 1 and 50: 0\n",
      "Enter a number between 1 and 50: 5\n",
      "The square of 1 is 1\n",
      "The square of 2 is 4\n",
      "The square of 3 is 9\n",
      "The square of 4 is 16\n",
      "The square of 5 is 25\n"
     ]
    }
   ],
   "source": [
    "## ANSWER EXERCISE 4 GOING FURTHER\n",
    "\n",
    "num = 0\n",
    "\n",
    "while num>50 or num<1:\n",
    "    num = int(input(\"Enter a number between 1 and 50: \"))\n",
    "\n",
    "i=1\n",
    "while i<=num:\n",
    "    print(\"The square of\", i, \"is\", i*i)\n",
    "    i+=1"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "0c4d8e57",
   "metadata": {},
   "source": [
    "### Exercise 5\n",
    "\n",
    "Write a python function that receives a whole number from user input, and calculates and print its factorial. The factorial is defined as follows:\n",
    "\n",
    "```\n",
    "n * (n - 1) * (n-2) * (n-3) * ... * (1).\n",
    "\n",
    "```\n",
    "\n",
    "The factorial of 7, for example, is:\n",
    "\n",
    "```\n",
    "7 * 6 * 5 * 4 * 3 * 2 * 1 = 5040\n",
    "```\n",
    "\n",
    "Note that there is a special case: the factorial of 0 is 1.\n",
    "\n",
    "Your code must use a while loop."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "id": "08a8c395",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Enter a whole number: 0\n",
      "1\n"
     ]
    }
   ],
   "source": [
    "# ANSWER EXERCISE 5\n",
    "\n",
    "num = int(input(\"Enter a whole number: \"))\n",
    "    \n",
    "if num==0:\n",
    "    print(\"1\")\n",
    "else:\n",
    "    factorial = 1\n",
    "    while num>0:\n",
    "        factorial = factorial*num\n",
    "        num-=1\n",
    "    print(factorial)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "6291f116",
   "metadata": {},
   "source": [
    "### Exercise 6\n",
    "\n",
    "Write code that prompts the user to input a whole number from 1 to 5. If the user enters a number that is not within this range, prompt them to re-enter a number until an appropriate value is entered. \n",
    "\n",
    "When an appropriate number is received, print the number in word form, e.g. for the number `4`, print `four`."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 12,
   "id": "679861a1",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Enter a number between 1 and 5: 8\n",
      "Enter a number between 1 and 5: 0\n",
      "Enter a number between 1 and 5: 3\n",
      "three\n"
     ]
    }
   ],
   "source": [
    "## ANSWER EXERCISE 6\n",
    "\n",
    "num = 0\n",
    "\n",
    "while num >5 or num<1:\n",
    "    num = int(input(\"Enter a number between 1 and 5: \"))\n",
    "\n",
    "if num == 1:\n",
    "    print(\"one\")\n",
    "elif num == 2:\n",
    "    print(\"two\")\n",
    "elif num ==3:\n",
    "    print(\"three\")\n",
    "elif num == 4:\n",
    "    print(\"four\")\n",
    "else:\n",
    "    print(\"five\")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "51c2d079",
   "metadata": {},
   "outputs": [],
   "source": []
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": "Python 3 (ipykernel)",
   "language": "python",
   "name": "python3"
  },
  "language_info": {
   "codemirror_mode": {
    "name": "ipython",
    "version": 3
   },
   "file_extension": ".py",
   "mimetype": "text/x-python",
   "name": "python",
   "nbconvert_exporter": "python",
   "pygments_lexer": "ipython3",
   "version": "3.10.9"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 5
}